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Date:   Tue, 24 Nov 2020 17:20:37 -0600
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Cc:     Bjorn Helgaas <bhelgaas@google.com>, Rob Herring <robh@kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Jingoo Han <jingoohan1@gmail.com>,
        Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
        Marc Zyngier <maz@kernel.org>, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Jassi Brar <jaswinder.singh@linaro.org>,
        Masami Hiramatsu <mhiramat@linaro.org>,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v8 3/3] PCI: uniphier: Add misc interrupt handler to
 invoke PME and AER
Message-ID: <20201124232037.GA595463@bjorn-Precision-5520>
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In-Reply-To: <1603848703-21099-4-git-send-email-hayashi.kunihiko@socionext.com>
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On Wed, Oct 28, 2020 at 10:31:43AM +0900, Kunihiko Hayashi wrote:
> This patch adds misc interrupt handler to detect and invoke PME/AER event.
> 
> In UniPhier PCIe controller, PME/AER signals are assigned to the same
> signal as MSI by the internal logic. These signals should be detected by
> the internal register, however, DWC MSI handler can't handle these signals.

I don't know what "PME/AER signals are assigned to the same signal as
MSI" means.  

I'm trying to figure out if this is talking about PME/AER MSI vector
numbers (probably not) or some internal wire that's not
architecturally visible or what.

Probably also not related to the fact that PME, hotplug, and bandwidth
notifications share the same MSI/MSI-X vector.

Is this something that's going to be applicable to all the DWC-based
drivers?

> DWC MSI handler calls .msi_host_isr() callback function, that detects
> PME/AER signals with the internal register and invokes the interrupt
> with PME/AER vIRQ numbers.
> 
> These vIRQ numbers is obtained from portdrv in uniphier_add_pcie_port()
> function.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Jingoo Han <jingoohan1@gmail.com>
> Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
> ---
>  drivers/pci/controller/dwc/pcie-uniphier.c | 77 +++++++++++++++++++++++++-----
>  1 file changed, 66 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-uniphier.c b/drivers/pci/controller/dwc/pcie-uniphier.c
> index 4817626..237537a 100644
> --- a/drivers/pci/controller/dwc/pcie-uniphier.c
> +++ b/drivers/pci/controller/dwc/pcie-uniphier.c
> @@ -21,6 +21,7 @@
>  #include <linux/reset.h>
>  
>  #include "pcie-designware.h"
> +#include "../../pcie/portdrv.h"
>  
>  #define PCL_PINCTRL0			0x002c
>  #define PCL_PERST_PLDN_REGEN		BIT(12)
> @@ -44,7 +45,9 @@
>  #define PCL_SYS_AUX_PWR_DET		BIT(8)
>  
>  #define PCL_RCV_INT			0x8108
> +#define PCL_RCV_INT_ALL_INT_MASK	GENMASK(28, 25)
>  #define PCL_RCV_INT_ALL_ENABLE		GENMASK(20, 17)
> +#define PCL_RCV_INT_ALL_MSI_MASK	GENMASK(12, 9)
>  #define PCL_CFG_BW_MGT_STATUS		BIT(4)
>  #define PCL_CFG_LINK_AUTO_BW_STATUS	BIT(3)
>  #define PCL_CFG_AER_RC_ERR_MSI_STATUS	BIT(2)
> @@ -68,6 +71,8 @@ struct uniphier_pcie_priv {
>  	struct reset_control *rst;
>  	struct phy *phy;
>  	struct irq_domain *legacy_irq_domain;
> +	int aer_irq;
> +	int pme_irq;
>  };
>  
>  #define to_uniphier_pcie(x)	dev_get_drvdata((x)->dev)
> @@ -167,7 +172,15 @@ static void uniphier_pcie_stop_link(struct dw_pcie *pci)
>  
>  static void uniphier_pcie_irq_enable(struct uniphier_pcie_priv *priv)
>  {
> -	writel(PCL_RCV_INT_ALL_ENABLE, priv->base + PCL_RCV_INT);
> +	u32 val;
> +
> +	val = PCL_RCV_INT_ALL_ENABLE;
> +	if (pci_msi_enabled())
> +		val |= PCL_RCV_INT_ALL_INT_MASK;
> +	else
> +		val |= PCL_RCV_INT_ALL_MSI_MASK;

I'm confused about how this works.  Root Ports can signal AER errors
with either INTx or MSI.  This is controlled by the architected
Interrupt Disable bit and the MSI/MSI-X enable bits (I'm looking at
PCIe r5.0, sec 6.2.4.1.2).

The code here doesn't look related to those bits.  Does this code mean
that if pci_msi_enabled(), the Root Port will always signal with MSI
(if MSI Enable is set) and will *never* signal with INTx?

> +	writel(val, priv->base + PCL_RCV_INT);
>  	writel(PCL_RCV_INTX_ALL_ENABLE, priv->base + PCL_RCV_INTX);
>  }
>  
> @@ -231,28 +244,52 @@ static const struct irq_domain_ops uniphier_intx_domain_ops = {
>  	.map = uniphier_pcie_intx_map,
>  };
>  
> -static void uniphier_pcie_irq_handler(struct irq_desc *desc)
> +static void uniphier_pcie_misc_isr(struct pcie_port *pp, bool is_msi)
>  {
> -	struct pcie_port *pp = irq_desc_get_handler_data(desc);
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>  	struct uniphier_pcie_priv *priv = to_uniphier_pcie(pci);
> -	struct irq_chip *chip = irq_desc_get_chip(desc);
> -	unsigned long reg;
> -	u32 val, bit, virq;
> +	u32 val;
>  
> -	/* INT for debug */
>  	val = readl(priv->base + PCL_RCV_INT);
>  
>  	if (val & PCL_CFG_BW_MGT_STATUS)
>  		dev_dbg(pci->dev, "Link Bandwidth Management Event\n");
> +

Looks like a spurious whitespace change?

>  	if (val & PCL_CFG_LINK_AUTO_BW_STATUS)
>  		dev_dbg(pci->dev, "Link Autonomous Bandwidth Event\n");
> -	if (val & PCL_CFG_AER_RC_ERR_MSI_STATUS)
> -		dev_dbg(pci->dev, "Root Error\n");
> -	if (val & PCL_CFG_PME_MSI_STATUS)
> -		dev_dbg(pci->dev, "PME Interrupt\n");
> +
> +	if (is_msi) {
> +		if (val & PCL_CFG_AER_RC_ERR_MSI_STATUS) {
> +			dev_dbg(pci->dev, "Root Error Status\n");
> +			if (priv->aer_irq)
> +				generic_handle_irq(priv->aer_irq);
> +		}
> +
> +		if (val & PCL_CFG_PME_MSI_STATUS) {
> +			dev_dbg(pci->dev, "PME Interrupt\n");
> +			if (priv->pme_irq)
> +				generic_handle_irq(priv->pme_irq);
> +		}
> +	}
>  
>  	writel(val, priv->base + PCL_RCV_INT);
> +}
> +
> +static void uniphier_pcie_msi_host_isr(struct pcie_port *pp)
> +{
> +	uniphier_pcie_misc_isr(pp, true);
> +}
> +
> +static void uniphier_pcie_irq_handler(struct irq_desc *desc)
> +{
> +	struct pcie_port *pp = irq_desc_get_handler_data(desc);
> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> +	struct uniphier_pcie_priv *priv = to_uniphier_pcie(pci);
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	unsigned long reg;
> +	u32 val, bit, virq;
> +
> +	uniphier_pcie_misc_isr(pp, false);
>  
>  	/* INTx */
>  	chained_irq_enter(chip, desc);
> @@ -329,6 +366,7 @@ static int uniphier_pcie_host_init(struct pcie_port *pp)
>  
>  static const struct dw_pcie_host_ops uniphier_pcie_host_ops = {
>  	.host_init = uniphier_pcie_host_init,
> +	.msi_host_isr = uniphier_pcie_msi_host_isr,
>  };
>  
>  static int uniphier_add_pcie_port(struct uniphier_pcie_priv *priv,
> @@ -337,6 +375,7 @@ static int uniphier_add_pcie_port(struct uniphier_pcie_priv *priv,
>  	struct dw_pcie *pci = &priv->pci;
>  	struct pcie_port *pp = &pci->pp;
>  	struct device *dev = &pdev->dev;
> +	struct pci_dev *pcidev;
>  	int ret;
>  
>  	pp->ops = &uniphier_pcie_host_ops;
> @@ -353,6 +392,22 @@ static int uniphier_add_pcie_port(struct uniphier_pcie_priv *priv,
>  		return ret;
>  	}
>  
> +	/* irq for PME */
> +	list_for_each_entry(pcidev, &pp->bridge->bus->devices, bus_list) {
> +		priv->pme_irq =
> +			pcie_port_service_get_irq(pcidev, PCIE_PORT_SERVICE_PME);
> +		if (priv->pme_irq)
> +			break;

Does this mean that all Root Ports must use the same MSI vector?  I
don't think that's a PCIe spec requirement, though of course DWC may
have its own restrictions.

I don't think this depends on CONFIG_PCIEPORTBUS, so it looks like
it's possible to have

  # CONFIG_PCIEPORTBUS is not set
  PCIE_UNIPHIER=y

in which case I think you'll have a link error.

> +	}
> +
> +	/* irq for AER */
> +	list_for_each_entry(pcidev, &pp->bridge->bus->devices, bus_list) {
> +		priv->aer_irq =
> +			pcie_port_service_get_irq(pcidev, PCIE_PORT_SERVICE_AER);
> +		if (priv->aer_irq)
> +			break;
> +	}
> +
>  	return 0;
>  }
>  
> -- 
> 2.7.4
> 
> 
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